fs/aio: Make io_cancel() generate completions again

The following patch accidentally removed the code for delivering
completions for cancelled reads and writes to user space: "[PATCH 04/33]
aio: remove retry-based AIO"
(https://lore.kernel.org/all/1363883754-27966-5-git-send-email-koverstreet@google.com/)
>From that patch:

-	if (kiocbIsCancelled(iocb)) {
-		ret = -EINTR;
-		aio_complete(iocb, ret, 0);
-		/* must not access the iocb after this */
-		goto out;
-	}

This leads to a leak in user space of a struct iocb. Hence this patch
that restores the code that reports to user space that a read or write
has been cancelled successfully.

Fixes: 41003a7bcfed ("aio: remove retry-based AIO")
Cc: Christoph Hellwig <hch@lst.de>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Sandeep Dhavale <dhavale@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: stable@vger.kernel.org
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240215204739.2677806-3-bvanassche@acm.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/aio.c b/fs/aio.c
index da18dbcfcb220864943ac7ecf2fd8637e1aa9e92..28223f51193123020166bb4a8a24dbac316943c6 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -2165,14 +2165,11 @@ COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id,
 #endif
 
 /* sys_io_cancel:
- *     Attempts to cancel an iocb previously passed to io_submit.  If
- *     the operation is successfully cancelled, the resulting event is
- *     copied into the memory pointed to by result without being placed
- *     into the completion queue and 0 is returned.  May fail with
- *     -EFAULT if any of the data structures pointed to are invalid.
- *     May fail with -EINVAL if aio_context specified by ctx_id is
- *     invalid.  May fail with -EAGAIN if the iocb specified was not
- *     cancelled.  Will fail with -ENOSYS if not implemented.
+ *     Attempts to cancel an iocb previously passed to io_submit(). If the
+ *     operation is successfully cancelled 0 is returned. May fail with
+ *     -EFAULT if any of the data structures pointed to are invalid. May
+ *     fail with -EINVAL if aio_context specified by ctx_id is invalid. Will
+ *     fail with -ENOSYS if not implemented.
  */
 SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
                struct io_event __user *, result)
@@ -2203,14 +2200,12 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
        }
        spin_unlock_irq(&ctx->ctx_lock);
 
-       if (!ret) {
-               /*
-                * The result argument is no longer used - the io_event is
-                * always delivered via the ring buffer. -EINPROGRESS indicates
-                * cancellation is progress:
-                */
-               ret = -EINPROGRESS;
-       }
+       /*
+        * The result argument is no longer used - the io_event is always
+        * delivered via the ring buffer.
+        */
+       if (ret == 0 && kiocb->rw.ki_flags & IOCB_AIO_RW)
+               aio_complete_rw(&kiocb->rw, -EINTR);
 
        percpu_ref_put(&ctx->users);